Radially loaded disc mounting system for a disc drive

ABSTRACT

A disc mounting system for mounting the discs of a disc drive in a fixed radial relationship to the hub of a spindle motor. The disc mounting system includes curved spring elements, having a substantially C-shaped cross section, which are curved on a radius greater than the radius of the central opening of the discs. One or more spring elements are utilized with each disc, and assembly tooling is used to bend the spring elements so that the discs, with the opening of the C-shaped springs engaging the inner diameter of the discs, can fit over the hub of the spindle motor. The assembly tooling is then removed to allow the spring elements to partially straighten, firmly engaging the discs relative to the spindle motor hub in the radial direction. In a first embodiment of the invention, alternative mechanisms are disclosed for establishing the axial positions of the discs. In a second embodiment, a plurality of annular grooves are provided in the spindle motor hub and the spring elements engage both the discs and annular grooves in the spindle motor hub to fixedly locate the discs relative to the spindle motor hub in both the radial and axial directions. Fabrication of the spring elements from a shape-memory alloy is also disclosed.

This application is a continuation application Ser. No. 08/931,808,filed on Sep. 16, 1997, now U.S. Pat. No. 6,055,123.

FIELD OF THE INVENTION

This invention relates generally to the field of hard disc drive datastorage devices, and more particularly, but not by way of limitation, toa new system for mounting the discs to the hub of a spindle motor in adisc drive.

BACKGROUND OF THE INVENTION

Disc drives of the type known as “Winchester” disc drives, or hard discdrives, are well known in the industry. Such disc drives magneticallyrecord digital data on a plurality of circular, concentric data trackson the surfaces of one or more rigid discs. The discs are typicallymounted for rotation on the hub of a brushless DC spindle motor. In discdrives of the current generation, the spindle motor rotates the discs atspeeds of up to 10,000 RPM.

Data are recorded to and retrieved from the discs by an array ofvertically aligned read/write head assemblies, or heads, which arecontrollably moved from track to track by an actuator assembly. Theread/write head assemblies typically consist of an electromagnetictransducer carried on an air bearing slider. This slider acts in acooperative hydrodynamic relationship with a thin layer of air draggedalong by the spinning discs to fly the head assembly in a closely spacedrelationship to the disc surface. In order to maintain the proper flyingrelationship between the head assemblies and the discs, the headassemblies are attached to and supported by head suspensions orflexures.

The actuator assembly used to move the heads from track to track hasassumed many forms historically, with most disc drives of the CurrentGeneration incorporating an actuator of the type referred to as a rotaryvoice coil actuator. A typical rotary voice coil actuator consists of apivot shaft fixedly attached to the disc drive housing base memberclosely adjacent the outer diameter of the discs. The pivot shaft ismounted such that its central axis is normal to the plane of rotation ofthe discs. An actuator bearing housing is mounted to the pivot shaft byan arrangement of precision ball bearing assemblies, and supports a flatcoil which is suspended in the magnetic field of an array of permanentmagnets, which are fixedly mounted to the disc drive housing basemember. On the side of the actuator bearing housing opposite to thecoil, the actuator bearing housing also typically includes a pluralityof vertically aligned, radically extending actuator head mounting arms,to which the head suspensions mentioned above are mounted. Whencontrolled DC current is applied to the coil, a magnetic field is formedsurrounding the coil which interacts with the magnetic field of thepermanent magnets to rotate the actuator bearing housing, with theattached head suspensions and head assemblies, in accordance with thewell-known Lorentz relationship. As the actuator bearing housingrotates, the heads are moved radially across the data tracks along anarcuate path.

Disc drives of the current generation are included in desk-top computersystems for office and home environments, as well as in laptop computerswhich, because of their portability, can be used wherever they can betransported. Because of this wide range of operating environments, thecomputer systems, as well as the disc drives incorporated in them, mustbe capable of reliable operation over a wide range of ambienttemperatures.

Furthermore, laptop computers in particular can be expected to besubjected to large amounts of mechanical shock as they are moved about.It is common in the industry, therefore, that disc drives be specifiedto operate over ambient temperature ranges of from, for instance, −5° C.to 60° C., and further be specified to be capable of withstandingoperating mechanical shocks of 100G or greater without becominginoperable.

One of the areas of disc drive design which is of particular concernwhen considering ambient temperature variations and mechanical shockresistance is the system used to mount the discs to the spindle motor.During manufacture, the discs are mounted to the spindle motor in atemperature- and cleanliness-controlled environment. Once mechanicalassembly of the disc drive is completed, special servo-writers are usedto prerecord servo information on the discs. This servo information isused during operation of the disc drive to control the positioning ofthe actuator used to move the read/write heads to the desired datalocation in a manner well known in the industry. Once the servoinformation has been recorded on the discs, it is assumed by the servologic that the servo information, and all data subsequently recorded,are on circular tracks that are concentric with relation to the spinaxis of the spindle motor. The discs, therefore, must be mounted to thespindle motor in a manner that prevents shifting of the discs relativeto the spindle motor due to differential thermal expansion of the discsand motor components over the specified temperature range, or due tomechanical shock applied to the host computer system.

Several systems for clamping of the discs to the spindle motor have beendescribed in U.S. Patents, including U.S. Pat. No. 5,528,434, issuedJun. 18, 1996, U.S. Pat. No. 5,517,376, issued May 14, 1996, U.S. Pat.No. 5,452,157, issued Sep. 19, 1995, U.S. Pat. No. 5,333,080, issuedJul. 26, 1994, U.S. Pat. No. 5,274,517, issued Dec. 28, 1993 and U.SPat. No. 5,295,030, issued Mar. 15, 1994, all assigned to the assigneeof the present invention and all incorporated herein by reference. Ineach of these incorporated disc clamping systems, the spindle motor ofthe disc drive includes a disc mounting flange extending radially fromthe lower end of the spindle motor hub. A first disc is placed over thehub during assembly and brought to rest on this disc mounting flange. Anarrangement of disc spacers and additional discs are then alternatelyplaced over the spindle motor hub until the intended “disc stack” isformed. Finally, some type of disc clamp is attached to the spindlemotor hub which exerts an axial clamping force against the uppermostdisc in the disc stack. This axial clamping force is passed through thediscs and disc spacers and squeezes the disc stack between the discclamp and the disc mounting flange on the spindle motor hub.

From the above description, it would appear that the only element thatwould need to be considered when designing a disc clamping system wouldbe the disc clamp, with any requirement for additional clamping forcebeing met by an increase in the strength of the disc clamp. However,with the industry trend of size reduction in the overall disc drive, thesize of various components within the disc drive has also been reduced.including the thickness of the discs. As the discs halve grown thinner,the amount of clamping force that can be applied to the discs withoutcausing, mechanical distortion of the discs has also fallen. That is,due to inescapable tolerance variation in the flatness of the discmounting flange on the spindle motor, the discs themselves and the discspacers between adjacent discs, as well as the yield strength of thedisc material, only a finite amount of axial clamping force can beapplied to the inner diameters of the disc before the desired flatnessof the disc surfaces is lost.

Furthermore, the amount of non-operating mechanical shock which the discdrive is specified to withstand is constantly being increased, withfuture disc drive products being considered which must be capable ofoperating after experiencing non-operating mechanical shocks in therange of 1000G.

In light of these facts, it is clear that the currently common practiceof axially loading the disc stack to prevent shifting of the discsrelative to the spindle motor hub has nearly reached its maximum usefulextreme, and a new system for mounting the discs to the spindle motorhub must be provided.

SUMMARY OF THE INVENTION

The present invention is a disc mounting system for mounting the discsof a disc drive in a fixed radial relationship to the hub of a spindlemotor. The disc mounting system includes curved spring elements, havinga substantially C-shaped cross section, which are curved on a radiusgreater than the radius of the central opening of the discs. One or morespring elements are utilized with each disc, and assembly tooling isused to bend the spring elements so that the discs, with the opening ofthe C-shaped springs engaging the inner diameter of the discs, can fitover the hub of the spindle motor. The assembly tooling is then removedto allow the spring elements to partially straighten, firmly engagingthe discs relative to the spindle motor hub in the radial direction. Ina first embodiment of the invention, alternative mechanisms aredisclosed for establishing the axial positions of the discs. In a secondembodiment, a plurality of annular grooves are provided in the spindlemotor hub and the spring elements engage both the discs and annulargrooves in the spindle motor hub to fixedly locate the discs relative tothe spindle motor hub in both the radial and axial directions.Fabrication of the spring elements from a shape-memory alloy is alsodiscussed.

It is a object of the invention to provide a system for mounting thediscs in a disc stack to the hub of a spindle motor used to rotate thediscs in a disc drive.

It is another object of the invention to provide a disc mounting systemwhich prevents shifting of the discs relative to the hub of the spindlemotor due to differential thermal expansion.

It is another object of the invention to provide a disc mounting systemwhich prevents shifting of the discs relative to the hub of the spindlemotor due to the applications of large mechanical shocks.

It is another object of the invention to provide a disc mounting systemthat is suitable for use in a high volume manufacturing operation.

It is another object of the invention to provide a disc mounting systemthat can be implemented in a high volume manufacturing operation in aneconomical manner.

The manner in which these objects are achieved, as well as otherfeatures and benefits of the invention, can best be understood by areview of the following DETAILED DESCRIPTION OF THE INVENTION, when leadin conjunction with an examination of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a prior art disc drive in which the presentinvention is particularly useful.

FIGS. 2-1 and 2-2 are simplified sectional elevation views of typicalprior art disc mounting systems which utilize only axial loading tosecure the discs.

FIG. 3 is a perspective view of a spring element that is a portion ofthe present invention.

FIG. 4 is a detail cross sectional view of the spring element of FIG. 3identifying specific features of the spring element.

FIG. 5 is an elevation view, partially in section, of a spindle motorhub which has been modified in accordance with a first embodiment of thepresent invention.

FIG. 6 is an elevation view of an assembly tool utilized in themanufacture of a disc drive incorporating the present invention.

FIGS. 7-1 through 7-4 are plan views illustrating steps in the assemblyof a disc drive incorporating a first embodiment of the presentinvention.

FIG. 8 is a simplified sectional elevation view of a disc stackassembly, illustrating two variations of the first embodiment of thepresent invention.

FIG. 9 is a top perspective view of a bottom disc spacer which is aportion of one variation of the first embodiment of the presentinvention.

FIGS. 10-1 and 10-2 are top and bottom perspective views, respectively,of an intermediate disc spacer which is a portion of one variation ofthe first embodiment of the present invention.

FIG. 11 is a bottom perspective view of a shrink-fit disc clamp which isa portion of one variation of the first embodiment of the presentinvention.

FIGS. 12-1 and 12-2 are detail sectional views illustrating the finalassembled relationship between components of one variation of the firstembodiment of the present invention.

FIG. 13 is an elevation view, partially in section, of a spindle motorhub which has been modified in accordance with a second embodiment ofthe present invention.

FIGS. 14-1 through 14-3 are plan views illustrating steps in theassembly of a disc drive incorporating a second embodiment of thepresent invention.

FIG. 15 is a simplified sectional elevation view of a disc stackassembly, illustrating the second embodiment of the present invention.

FIGS. 16-1 and 16-2 are detail sectional views illustrating the finalassembled relationship between components of the second embodiment ofthe present invention.

FIGS. 17-1 and 17-2 are detail sectional views illustrating a variationof the disc mounting system of the second embodiment of FIGS. 16-1 and16-2.

DETAILED DESCRIPTION OF THE INVENTION

Turning now the drawings and specifically to FIG. 1, shown is a planview of a disc drive 2 in which the present invention is particularlyuseful. The disc drive 2 includes a base member 4 to which all othercomponents are directly or indirectly mounted and a top cover 6 (shownin partial cutaway) which, together with the base member 4, forms a discdrive housing which encloses delicate internal components and isolatesthese components from external contaminants.

The disc drive includes a plurality of discs 8 which are mounted forrotation on a spindle motor shown generally at 10. The discs 8 includeon their surfaces a plurality of circular, concentric data tracks, theinnermost and outermost of which are shown by dashed lines at 12, onwhich data are recorded via an array of vertically aligned headassemblies (one of which is shown it 14). The head assemblies 14 aresupported by head suspensions, or flexures 16, which are attached toactuator head mounting arms 18. The actuator head mounting arms 18 areintegral to all actuator bearing housing 20 which is mounted via anarray of ball bearing assemblies (not designated) for rotation about apivot shaft 22.

Power to drive the actuator bearing housing 20 in its rotation about thepivot shaft 22 is provided by a voice coil motor (VCM) shown generallyit 24. The VCM 24 consists of a coil (not separately designated) whichis supported by the actuator bearing housing 20 within the magneticfield of an array of permanent magnet (also not separately designated)which are fixedly mounted to the base member 4, all in a manner wellknown in the industry. Electronic circuitry (partially shown at 26,generally, and partially carried on a printed circuit board (not shown))to control all aspects of the operation of the disc drive 2 is provided,with control signals to drive the VCM 24, as well as data signals to andfrom the heads 14, carried between the electronic circuitry and themoving actuator assembly via a flexible printed circuit cable (PCC) 28.

FIG. 2-1 is a simplified sectional elevation view of a typical prior artdisc mounting system which utilizes axial loading to secure the discs.The figure shows a hub 30 of a spindle motor having a radially extendingdisc mounting flange 32 at its lower extreme. The hub 30 issubstantially cup-shaped, being closed at the upper end and open at thelower end. The person of skill in the art will appreciate that theelectrical and magnetic components (not shown) to rotate the hub 30would typically be located within the hub.

FIG. 2-1 also shows a plurality of discs 8 and disc spacers 34. The discstack is assembled by placing a first disc 8 over the hub 30 to restagainst the disc mounting flange 32. The stack is formed by thenalternately placing disc spacers 34 and discs 8 over the hub until theintended number of discs 8 have been positioned. A disc clamp 36 is thenassembled to the uppermost portion of the hub 30 to complete theassembly. While the figure shows an example disc stack which includesfour discs, the person of skill in the art will appreciate that thescope of the present invention includes disc stacks having both greaterand lesser numbers of discs.

In FIG. 2-1, the disc clamp 36 is of the type referred to in theindustry as a “shrink-fit” clamp. Such clamps have an inner diameterthat is nominally smaller than the outer diameter of the hub 30.Assembly is accomplished by heating the clamp 36 to cause thermalexpansion great enough to allow the clamp 36 to pass over the hub 30.The designed amount of axial loading is then applied to the disc clamp36 and the clamp 36 is allowed to cool and shrink into interference fitwith the hub 30.

Turning to FIG. 2-2, shown is a simplified diagrammatic sectionalelevation view, similar to that of FIG. 2-1, showing a second prior artdisc clamping system. FIG. 2-2 shows a spindle motor hub 30Incorporating a disc mounting flange 32 similar to that shown in FIG.2-1, and a stack of discs 8 and disc spacers 34, also similar to thoseof FIG. 2-1.

FIG. 2-2 shows a disc clamp 40 of the type known in the industry as a“spring clamp”. Such spring disc clamps 40 are typically formed fromflat sheet stock having the desired spring characteristics and includecircumferential corrugations closely adjacent the outer diameter of thedisc clamp which form a contact surface (not designated) for exertingforce to the disc stack when a plurality of screws 42 are assembledthrough the disc clamp 40 into threaded holes (also not designated) inthe hub 30. It is also typical for disc clamping systems incorporatingsuch spring disc clamps 40 to include a washer member 44 between thecontact surface of the disc clamp 40 and the upper surface of theuppermost disc 8. This washer member 44 aids in evenly distributing theclamping force of the disc clamp 40 about the circumference of themounting portion of the discs 8 and allows for slip contact between thecontact surface of thie disc clamp 40 and the washer member 44 when thescrews 42 are tightened, thus preventing, the exertion of radialstresses directly to the uppermost disc 8.

Selection of the material and geometry of the disc clamp 40 willdetermine the amount of axial clamping force exerted by the discclamping system of FIG. 2-2, as will be appreciated by persons of skillin the art. Details of typical disc clamping systems incorporating aspring clamp such as that of FIG. 2-2 can be found in previouslyincorporated U.S. Pat. Nos. 5,274,517 and 5,295,030.

Both of these two prior art disc clamping systems share a commondrawback. Specifically, since the inner diameter of the discs must be atleast slightly larger than the outer diameter of the spindle motor hubto allow for assembly ease, the discs are subject to radial displacementrelative to the spindle motor hub after assembly due to differentialthermal expansion and applied mechanical shocks. And, since all clampingforces applied to the disc stack are in the axial directions allresistance to such radial shifting of the discs relative to the spindlemotor hub is, therefore, purely a function of the amount of appliedaxial force and the coefficient of friction of the disc stackcomponents. As previously noted hereinabove, with the continuing markettrend or higher and higher mechanical shock tolerances, such purelyaxially loaded disc mounting systems are becoming unsatisfactory.

FIG. 3 is a perspective view of a spring element 50 which is a majorcomponent in all embodiments of the present invention. The springelement 50 is substantially C-shaped in cross section and curved alongits length. As will be explained in detail below, the radius of thecurve of the spring element 50 is greater than the radius of the centralopening, or inner diameter, of the discs in the disc drive in which thepresent invention is implemented.

The spring element 50 can be seen to include end portions 52 and amiddle portion 54. The end portions 52 and middle portion 54 areparticularly important from a functional viewpoint, as will be seenbelow in the discussions of how the spring element 50 interacts withother elements of the disc drive to implement the invention.

It is presently envisioned that the spring element will be fabricatedfrom 300 series stainless steel, but any material having the desiredspring characteristics, as will be described below, is envisioned asfalling with the scope of the present invention. Furthermore, certainmaterials having shape-memory characteristics are particularlyenvisioned as being suitable for the spring element 50, as will also bediscussed below.

FIG. 4 is a cross sectional view of the spring element 50, and ispresented to identify specific features and surfaces of the springelement 50. In particular, the spring element 50 can be seen to includean inner radial surface 56 and an outer radial surface 58. The terms“inner” and “outer” in these designators relates to the center of a discstack mounted on the hub of a spindle motor. These radial surfaces 56,58 will interact with the spindle motor hub and the inner diameter ofthe discs in a manner to be discussed below.

The spring element also includes inner axial surfaces 60 and outer axialsurfaces 62. The inner axial surfaces 60 are separated by an inner axialdimension 64 selected to interact cooperatively with the thickness ofthe discs, while the outer axial surfaces 62 are separated by an outeraxial dimension 66, the size of which will be determined by certainother aspects of the implementation of the invention, as will bedescribed in detail below.

FIG. 5 is an elevation view, partially in section, of a spindle motorhub 30 a which has been modified in accordance with a first embodimentof the present invention. Specifically, the left half of FIG. 5 showsthe spindle motor hub 30 a in section, while the right half of thefigure shows the spindle motor hub 30 a in elevation view.

The spindle motor hub 30 a includes a radially extending disc mountingflange 32, similar to the disc mounting flange 32 of the prior art FIGS.2-1 and 2-2. The principle difference between the inventive spindlemotor hub 30 a of FIG. 5 and the prior art spindle motor hub 30 of FIGS.2-1 and 2-2 is the addition of axially extending tooling features 68distributed about the periphery of the spindle motor hub 30 a. Thesetooling features 68 are used in conjunction with a complementary numberof assembly tools, to be described below, to facilitate the assembly ofa disc drive incorporating the present invention, as will also bediscussed below. The specific number of tooling features 68 included inthe spindle motor hub 30 a is dependent on the particular embodiment ofthe present invention implemented in the disc drive, and is notconsidered as limiting to the scope of the present invention.

FIG. 6 is an elevation view of an assembly tool 70 used to facilitateassembly of a disc drive incorporating certain embodiments of thepresent invention. The assembly tool 70 includes a pre-mounting portion72, a ramp portion 74 and a hub portion 76 which acts cooperatively withthe tooling features 68 in the spindle motor hub. When employed duringthe assembly of a disc drive using the present invention, the hubportion 76 of the assembly tool 70 is inserted into the tooling feature68 in the spindle motor hub and the pre-mounting portion 72 ispositioned toward the center of the spindle motor hub. At the lowest endof the hub portion 76, the assembly tool includes a beveled end 78. Themanner in which the assembly tool 70 is used to facilitate assembly willbe discussed below.

FIGS. 7-1 through 7-4 are plan views of various elements of the discdrive showing their relationships during assembly. In FIG. 7-1, aportion of a disc 8 is shown, including the central opening 8 a. Thefigure also shows a plurality of spring elements 50 equally spaced aboutthe central opening, 8 a of the disc 8. While the figure specificallyshows four spring elements 50, a person of skill in the art will realizethat the particular number of spring elements 50 is a matter of designchoice, and should not be considered as limiting to the scope of theinvention.

In FIG. 7-1 it can be seen that the spring elements have been placedover the inner edge of the disc 8. Because, as previously noted, theradius of the spring elements 50 is greater than the radius of thecentral opening 8a in the disc 8, the outer radial surface 58 of thespring elements 50 contacts the disc 8 only at the end portions 52 ofthe spring elements 50, and is not in contact with the disc 8 in themiddle portion 54 of the spring elements 50.

FIG. 7-2 shows a spindle motor hub 30 a similar to that shown in FIG. 5.The spindle motor hub 30 a includes a plurality of axially extendingtooling features 68 distributed about the outer diameter of the hub 30a. In the example shown in FIG. 7-2, there are four tooling features 68to cooperate with the four spring elements 50 of FIG. 7-1, but theperson of skill in the art will appreciate that the actual number oftooling features 68 will be dependent on the number of spring elements50 included in the particular implementation, and, as such is notconsidered as limiting to the invention.

FIG. 7-2 also shows an assembly tool 70, such as that of FIG. 6,inserted in each of the tooling features 68. The assembly tools 70 arepositioned in the tooling features 68 with their pre-mounting portions(72 in FIG. 6) rotated to lie toward the center of the spindle motor hub30 a. Thus the ramp portion (74 in FIG. 6) slopes radially outward as itextends from the pre-mounting portion 72 to the hub portion 76 whichengages the tooling features 68. Thus, the radially outermost surfacesof the combined assembly tools 70 form a first, small diameter cylinderat the pre-mounting portions 72 connected to a conical portion in thearea of the ramp portions 74 which increases in diameter from thepre-mounting portion 72 to the hub portions 76. The radially outermostsurfaces of the hub portions 76 extends slightly beyond the outerdiameter of the spindle motor hub 30 a in the region of the toolingfeatures 68.

Assembly is accomplished by placing the disc 8, with spring, elements 50installed on the inner diameter of the disc as in FIG. 7-1, over theassembly tools 70, and lowering the disc 8 until the middle portions (54in FIG. 3) of the inner radial surfaces of the spring elements (56 inFIG. 4) contact the ramp portions 74 of the assembly tools 70. The disc8 is then pressed downward toward the spindle motor hub 30 a. As thedisc 8 is pressed downward, the spring elements 50 are bent outwarduntil, when the disc 8 reaches the hub portions 76 of the assembly tools70, the innermost portions of the spring elements 50 lie outside thediameter of the spindle motor hub 30 a. This component relationship isshown in FIG. 7-3.

FIG. 7-3 shows the disc 8 with the spring elements 50 bent outward bycontact with the hub portions of the assembly tools 70 to all extentwhere the spring elements 50 can pass over the spindle motor hub 30 a.In this position, the outer radial surface (58 in FIG. 4) of the springelements 50 are bent into substantial contact with the inner diameter 8a of the disc 8. Once the disc mounting system components are in thisrelationship, the disc 8 can be pressed downward along the hub portions76 of the assembly tools 70 to the desired axial position on the spindlemotor hub. Example embodiments of component relationships fordetermining the axial position of the discs on the spindle motor hub 30a will be discussed below.

FIG. 7-4 shows the final assembled relationship of components. In FIG.7-4, the assembly tools (70 in FIGS. 7-2 and 7-3) have been axiallywithdrawn from their engagement with the tooling features 68 of thespindle motor hub 30 a. As the assembly tools 70 are pulled from the hub30 a, the beveled ends (78 in FIG. 6) of the assembly tools 70 allow thespring elements 50 to straighten. As the spring elements 50 straighten,the middle portion (54 in FIG. 3) of the inner radial surfaces (56 inFIG. 4) of the spring elements 50 come into contact with the outerdiameter of the spindle motor hub 30 a in the region of the toolingfeatures 68. Meanwhile, contact is maintained between the outer radialsurface (58 in FIG. 4) of the spring elements 50 and the disc 8 in thearea of the end portions (52 in FIG. 3) of the spring elements 50. Fixedradial positioning of the disc 8 relative to the spindle motor hub 30 ais established by contact between the middle portion 54 of the springelements 50 and the spindle motor hub 30 a, and by contact between theend portions 52 of the spring elements and the inner diameter 8 a of thedisc 8.

FIG. 8 is a sectional elevation view of a disc stack taken along lineA-A′ of FIG. 7-4 showing two alternatives for establishing the axialposition of the discs 8 relative to the spindle motor hub 30 a. In bothalternatives, the spindle motor hub 30 a includes a radially extendingdisc mounting flange 32 similar to the prior art hub 30 of FIGS. 2-1 and2-2.

On the left side of FIG. 8, it can be seen that the axial dimension (66in FIG. 4) of the spring elements 50 have been selected to establish thedesired inter-disc spacing. That is, the lowermost disc 8 is presseddownward until the spring elements 50 come into contact with the discmounting flange 32, and subsequent discs are pressed downward until thespring elements 50 associated with the discs 8 contact the springelements 50 of the next-lower disc 8 in the disc stack. Finally, a discclamp 36 a is mounted to the uppermost portion of the spindle motor hub30 a. The disc clamp 36 a is of the shrink-fit type previously describedin relationship to prior art FIG. 2-1, but could also be a spring-typedisc clamp as described in relationship to prior art FIG. 2-2. Thesignificant difference between the disc mounting system illustrated onthe left side of FIG. 8 and the prior art of FIGS. 2-1 and 2-2 is thatthe disc clamp 36 a only has to provide sufficient axial loading to meetthe axial shock requirement of the disc drive, and all radialpositioning of the discs is established and maintained by the springelements 50.

One potential drawback to the disc mounting system shown on the leftside of FIG. 8 is that the discs 8 are only supported by the springelements 50 and are free-floating between the spring elements 50. Whilethis disc mounting system may be entirely adequate for some disc drives,other disc drives may require more support of the discs about thediameter of the spindle motor 30 a.

The right side of FIG. 8 shows an alternative disc mounting system whichprovides additional axial support of the discs 8 relative to the spindlemotor hub 30 a. The disc mounting system of the right side of FIG. 8includes spring elements 50 operating as previously described inrelationship to FIGS. 7-1 through 7-4 above. That is, the springelements 50 contact the spindle motor hub 30 a in the area of thetooling features 68 and also contact and radially position the discs 8relative to the spindle motor hub 30 a.

The disc mounting system shown on the right side of FIG. 8 also includesa specially configured bottom disc spacer 80, a plurality of speciallyconfigured intermediate disc spacers 82 and a specially configured discclamp 36 b. The features of the bottom disc spacer 80, intermediate discspacers and disc clamp 36 b will be described in detail, and theassembled relationship of these components will then be described below.

FIG. 9 is a top perspective view of a bottom disc clamp 80 used in thedisc mounting system of the right side of FIG. 8. The bottom disc clamp80 includes a flat bottom surface 84 intended for cooperative engagementwith the upper surface of the disc mounting flange (32 in FIG. 8). Thebottom disc spacer 80 also includes an axially extending inner wall 86interrupted at intervals by notches 88 intended to interact with thespring elements 50. In the example configuration shown, there are fournotches for cooperation with a complementary number of spring elements,such as the configuration of components shown in FIGS. 7-1 through 7-4.A person of skill in the art will, however, appreciate that the specificnumber of spring elements 50, and thus notches 88 is a matter of designchoice and should not be considered as limiting to the scope of theinvention.

The bottom disc spacer 80 also includes a disc contact surface 90intended to engage the inner portion of the discs 8 as shown on theright side of FIG. 8. The disc contact surface 90 includes anappropriate number of recesses 92 associated with the notches 88 toaccommodate the spring elements 50.

FIGS. 10-1 and 10-2 are top and bottom perspective views, respectively,of an intermediate disc spacer 82. In the figures it can be seen thatthe intermediate disc spacer 82 includes an upper disc contact surface94 a and a lower disc contact surface 94 b separated by a vertical wall96 dimensioned to provide the desired amount of inter-disc spacing. Boththe upper and lower disc contact surfaces 94 a, 94 b include anappropriate number of recesses 98 to accommodate the spring elements 50.

The intermediate disc spacer 82 also includes an axially extending innerwall 100, similar to the inner wall 86 of the bottom disc spacer 80 ofFIG. 9. The inner wall 100 of the intermediate disc spacer 82 is alsointerrupted at intervals by notches 102, similar in configuration andfunction to the notches 88 in the inner wall 86 of the bottom discspacer 80 of FIG. 9.

Finally, the intermediate disc spacer 82 includes an annular step 104.This annular step 104 is intended for cooperation with the top of theinner wall of the next lower element in the disc stack, as will bedescribed below.

FIG. 11 is a bottom perspective view of a disc clamp 36 b which is thefinal component in the disc mounting system of the right side of FIG. 8.Again, the disc clamp 36 b is a shrink-fit type disc clamp, and thus hasan inner diameter 36 c which is nominally smaller than the outerdiameter of the spindle motor hub to which it is intended to mount.Assembly is accomplished by first heating the disc clamp 36 b to causeit to expand, placing the disc clamp 36 b over the spindle motor hubinto its intended position and allowing the disc clamp 36 b to cool andcontract into contact with the outer diameter of the spindle motor hub.It should be noted that the bottom disc spacer 80 of FIG. 9 and theintermediate disc spacer 82 of FIGS. 10-1 and 10-2 have an innerdiameter which is nominally slightly larger than the outer diameter ofthe spindle motor hub to allow ease of assembly.

The disc clamp 36 b has a lower surface configured similarly to theintermediate disc spacer 82. That is, the disc clamp 36 b includes adisc contact surface 94 c interrupted by an appropriate number ofrecesses 98 to cooperate with the spring elements 50, and an annularstep for cooperation with the inner wall of the disc spacer below thedisc clamp 36 b in the disc stack. The manner in which the components ofthe disc mounting system of the right side of FIG. 8 interact in theirassembled condition will now be described.

FIGS. 12-1 and 12-2 are detail sectional views, taken along lines B-B′and C-C′, respectively, of FIG. 7-4, showing the interaction of the discstack components of the disc mounting system of the right side of FIG.8.

FIG. 12-1 shows a sectional view through the middle portion of thespring elements 50, and shows that the inner radial surfaces (56 in FIG.4) of the spring elements 50 are in direct contact with the spindlemotor hub 30 a. The bottom disc spacer 80 is seen to rest directly onthe disc mounting flange 32 of the spindle motor hub 30 a.

The discs 8 are axially positioned by contact between the discs 8 andthe disc contact surfaces 90, 94 a, 94 b of the bottom and intermediatedisc spacers 80, 82. As can be seen in the figure, the recesses 92, 98in the disc contact surfaces 90, 94 a, 94 b are dimensioned to allowclearance between the disc spacers 80, 82 and the spring elements 50.This spacing ensures that axial positioning of the discs 8 is controlledonly by contact between the discs and the disc contact surfaces 90, 94a, 94 b of the disc spacers 80, 82.

Although it appears that the inner diameters of the discs 8 are notradially constrained by the spring elements 50 in FIG. 12-1, it shouldbe recalled that FIG. 12-1 is taken along line B-B′ of FIG. 7-4, andthus is showing the middle portion (54 in FIG. 3) of the spring elements50. At the end portions (52 in FIG. 3) of the spring elements 50, theouter radial surface (58 in FIG. 4) will directly contact the innerdiameters of the discs 8, radially positioning the discs 8 relative tothe spindle motor hub.

FIG. 12-2 is a detail sectional view taken along line C-C′ of FIG. 7-4,showing the relationship of the disc stack components in the areabetween spring elements 50. In the figure, it can be seen that thebottom disc spacer 80 rests directly on the disc mounting flange 32 ofthe spindle motor hub 30a, and that axial positioning of the discs 8 isdetermined solely by contact between the discs and the disc contactsurfaces 90, 94 a, 94 b of the bottom and intermediate disc spacers 80,82.

FIG. 12-2 also shows that the inner walls 86, 100 of the bottom andintermediate disc spacers 80, 82 are radially dimensioned to not contactthe inner diameter of the discs 8, or the spindle motor hub 30 a. Thisis because the radial position of the discs 8 relative to the spindlemotor hub is determined by the spring elements 50, and there must besome assembly dimensional tolerance to allow the disc spacers 80, 82 tobe placed over the spindle motor hub 30 a. Similarly, the inner walls86, 100 and annular steps 104 in the intermediate disc spacers 82 aredimensioned to preclude direct contact, again ensuring that the axialpositioning of the discs 8 relative to the spindle motor hub 30 a issolely a function of the disc spacer disc contact surfaces 90, 94 a, 94b.

One of skill in the art will appreciate that the bottom disc spacer 80could be eliminated from the disc stack, thus reducing the overallheight of the disc stack, if the disc mounting flange 32 were modifiedto include recesses to accommodate the spring elements on the lowermostdisc 8 in the disc stack. Similarly, since the inner walls 86, 100 ofthe bottom and intermediate disc spacers do not contact adjacentelements in the disc stack other than the discs 8, the disc spacers 80,82 could be fabricated without these features.

A person of skill in the art will also appreciate that either variationof the first embodiment of the invention can be implemented using asingle spring element 50 for each disc. In such a configuration, a pointon the inner diameter of the disc radially opposite the spring elementwill be biased into direct contact with the spindle motor hub. It shouldbe pointed out, however, that such an approach will cause the disc to bemounted off-center to the spindle motor hub, potentially leading to anunbalancing of the disc stack. This unbalancing can, however, becompensated for in disc drives having more than one disc bycircumferentially displacing the spring elements of each disc from thespring elements of other discs in the disc stack by an angle dependenton the number of discs. For instance, in a disc drive including twodiscs, the spring elements would be displaced 180 degrees from eachother, while a disc drive having three discs would displace the springelements by 120 degrees. Fine tuning of the balancing of the entirestack may require minor deviation from equiangular displacement of thespring members, or modification of the angular displacement of thespring element location dependent on the axial position of theassociated disc. Such balancing is believed to be within the expertiseof a person of normal skill in the art.

In another aspect of the present invention, it is envisioned that thespring elements 50 used to radially load the discs 8 relative to thespindle motor hub are fabricated from a shape-memory alloy (SMA). SMAsare well known in the industry, and are typically characterized byhaving two distinct crystalline states or phases, each of which isachieved at specific temperatures dependent on the exact alloycomposition and the fabrication processes used in the manufacture ofcomponents. The first of these two phases, the martensitic phase, ischaracterized by occurring at a lower temperature range than the second,or austenitic, phase. The martensitic phase is also typically “weaker”or more malleable than the austenitic phase. The austenitic phase issometimes referred to as the “trained” phase. If a SMA component isformed to a particular shape and heated to a transition temperature(dependent upon alloy composition) while held in that shape, thecomponent forms with a “memory” of that shape. When allowed to cool, thematerial switches to the martensitic phase, and can be bent or deformedwith relative ease. If the component is then heated to an activationtemperature (again dependent on alloy composition), the component againtransforms to its austenitic phase, and recovers the shape in which itwas originally “trained”. This phase and shape change is accomplishedwith a high level of force.

The applicability of SMAs to the present invention relates to thefabrication of the spring elements 50. If the spring elements 50 areformed and trained with a curvature greater than the radius of the innerdiameter of the discs, and then allowed to cool, they can bemechanically shaped to conform to the radius of the inner diameter ofthe discs when mounted to the discs. In such condition, the springs willallow the discs, with the spring elements attached, to be readily placedover the hub of the spindle motor without the use of the assembly tools(70 in FIGS. 6, 7-2 and 7-3) as described above. Once the disc ispositioned at its desired axial location relative to the spindle motorhub, the spring elements are heated to their activation temperature, andwill straighten to recover their “memorized” shape. As the springelements straighten, the inner radial surface (56 in FIG. 4) near themiddle portion (54 in FIG. 3) of the spring element 50 will bear againstthe spindle motor hub, while the outer radial surface (58 in FIG. 4)near the end portions (52 in FIG. 3) of the spring elements 50 bearsagainst the inner diameter of the discs, thus establishing a fixedradial loading of the discs relative to the spindle motor hub.

In a second major embodiment of the present invention, the disc mountingflange 32 of the spindle motor hub 30 a can be eliminated entirely, thusproviding a lower height for the disc stack, or allowing more discs tobe mounted in the same vertical space. The features of this second majorembodiment of the invention will now be discussed.

FIG. 13 is an elevation view, partially in section, of a spindle motorhub 110 which is fabricated in accordance with a second embodiment ofthe present invention. As can be seen in the figure, the spindle motorhub 110 does not include a disc mounting flange as was present in theprior art spindle motor hubs 30 of FIGS. 2-1 and 2-2 and the spindlemotor hub 30 a of the first embodiment of the invention as illustratedin FIGS. 8, 12-1 and 12-2.

The outer diameter 112 of the spindle motor hub 110 is slightly smallerthan the inner diameter of the discs to be mounted, as will be discussedin more detail below, and the spindle motor hub 110 includes a pluralityof annular grooves 114 cast or machined into the hub 110. As will beillustrated below, the spindle motor hub 110 includes an annular groove114 for each disc mounted to the spindle motor, and the axial and radialdimensions of the annular grooves are selected to interact with otherelements of the disc mounting system in a manner which will also bediscussed below.

FIG. 13 also shows that the spindle motor hub 110 includes a number ofaxially extending tooling features 116 distributed circumferentiallyabout the outer diameter of the spindle motor hub 110. These toolingfeatures are similar in form and function to the tooling features 68 inthe previously described first embodiment, and are used in conjunctionwith the assembly tool 70 of FIG. 6 as will be described below.

FIGS. 14-1 through 14-3 are plan views of various components of a discdrive incorporating the second embodiment of the present invention,showing their relationships during assembly. In FIG. 14-1, a portion ofa disc 8 is shown with a pair of spring elements 50 engaged with theinner diameter 8 a of the disc 8. Once again, a person of skill in theart will realize that the specific number of spring elements 50 will bedetermined by considerations related to the total disc drive design,and, as such, should not be considered as being limiting to the scope ofthe invention.

In FIG. 14-1, it can be seen that the spring elements have a curveradius greater than the radius of the inner diameter 8 a of the disc 8,and, as such, the spring elements 50 are in contact with the innerdiameter 8 a of the disc 8 only at their end portions 52, while theouter radial surface 58 of the spring members 50 does not contact thedisc 8 near the middle portions (54 in FIG. 3). As in the springelements 50 of the previously described first embodiment, the springelements have an internal axial dimension (64 in FIG. 4) selected tocooperate closely with the thickness of the disc 8.

FIG. 14-2 is a plan view similar to that of FIG. 7-3 and shows therelationship of disc drive components when the disc 8 with associatedspring elements 50 has been placed over a pair of assembly tools 70inserted in the tooling features 116 in the spindle motor hub 110 andpressed down until the spring elements 50 are in contact with the hubportions (76 in FIG. 6) of the assembly tools 70. In the exampleassembly shown, other centering apparatus must be included to ensurethat the assembly tools 70 contact the spring elements 50 at the properpoint to align the disc 8 with the spindle motor hub. If, however, threeor more tooling features 116 and assembly tools 70 were to be used, thecentering of the disc 8 relative to the spindle motor hub 110 wouldaccomplished automatically.

FIG. 14-2 shows that when the discs 8 are axially positioned on the hubportion of the assembly tool 70, the inner radial surfaces 56 of thespring elements 50 have been displaced radially to a position radiallyoutward of the outer diameter of the spindle motor hub 110, allowing thediscs 8 with associated spring elements 50 to be axially positioned atthe desired location on the spindle motor hub 110.

FIG. 14-3 shows the final assembled relationship between elements of thesecond embodiment of the invention. When the assembly tools (70 in FIG.14-2) are removed from the tooling features 116 of the spindle motor hub110, the spring elements 50 are allowed to straighten as the beveledends (78 in FIG. 6) of the assembly tools 70 pass by the spring elements50. As the spring elements 50 straighten, the inner radial surfaces 56of the spring elements pass into and engage the annular grooves 114 inthe spindle motor hub 110, thus establishing the axial position of thedisc 8 relative to the spindle motor hub 110. Once again, as in thepreviously described first embodiment, the outer radial surfaces 58 ofthe spring elements 50 engage the discs 8 at the end portions 52 of thespring elements 50, providing radial positioning of the disc 8 relativeto the spindle motor hub 110.

FIG. 15 is a simplified sectional elevation view, taken along line D-D′of FIG. 14-3, of a disc stack constructed in accordance with the secondembodiment of the invention. As the figure shows, the discs are axiallyconstrained by the spring elements 50 and the relationship between thespring elements 50 and the annular grooves 114 in the spindle motor hub110. Details of the component relationships are shown in FIGS. 16-1 and16-2 and described below.

FIG. 16-1 shows in detail the relationship of components at the leftside of FIG. 15, that is, at the end of the D-D′ line of FIG. 14-3closest to the D end. In the figure, it can be seen that the innerradial surface 56 of the spring element 50 rests in contact with theinner surface of the annular groove 114 in the area of the toolingfeature 116 of the spindle motor hub 110. The outer axial surfaces 62 ofthe spring element 50 interact with cooperative axial surfaces 118 ofthe annular groove 114 to provide axial positioning of the disc 8, whichis captured between the inner axial surfaces 60 of the spring element50. Since FIG. 16-1 is a view at the middle portion (54 in FIG. 3) ofthe spring element 50, the inner diameter 8 a of the disc 8 is radiallydisplace from the outer radial surface 58 of the spring member 50.

FIG. 16-2 shows in detail the relationship of components at the rightside of FIG. 15, that is, at the end of the D-D′ line of FIG. 14-3closest to the D′ end. As can be seen in the figure, at the end portion52 of the spring element 50 outer radial surface 58 of the springelement 50 directly contacts the inner diameter 8 a of the disc 8. Theinner radial surface 56 of the spring element 50 is radially displacedfrom the annular groove 114 in the spindle motor hub 110 at thiscircumferential location, but it should be recalled that the middleportion of the spiring element 50 is firmly engaged with the annulargroove 114. Once again it should he noted that the inner axial surfaces60 of the spring element 50 directly contact the disc 8.

A person of skill in the art will appreciate that this second embodimentof the invention can also be implemented using spring elements 50fabricated from SMA, as described hereinabove. In such animplementation, the discs, with SMA spring elements 50 mounted on theirinner diameters, can be placed over the spindle motor hub 110 withoutthe need for the assembly tools 70 and associated assembly features 116in the spindle motor hub. Again, once the discs are positioned at theirdesired axial locations relative to the spindle motor hub 110, thespring elements 50 would then be heated to return the spring elements totheir straighter memory condition, radially fixing the discs 8 inrelationship to the spindle motor hub 110.

FIGS. 17-1 and 17-2 are detail sectional views of a variation of thesecond embodiment of the present invention. FIGS. 17-1 and 17-2 aresimilar to the views of FIGS. 16-1 and 16-2 discussed above. That is,FIG. 17-1 is a sectional view taken through the middle portion (54 inFIG. 3) of a spring element 50 a in the region of the tooling feature116 in the spindle motor hub 110, while FIG. 17-2 is a sectional viewtaken adjacent an end portion (52 in FIG. 3) of a spring element 50 a.

In FIGS. 17-1 and 17-2, the annular grooves 114 a in the spindle motorhub 110 have an arcuate shape, while the inner radial surface 56 a andouter radial surface 58 a of the spring element 50 a are also formed inan arc. The arcs of the inner radial surface 56 a and outer radialsurface 58 a are formed with a radius greater than the radius of theannular groove 114 a. As can be seen in FIG. 17-1, this relationshipbetween the arc radii of the inner radial surface 56 a of the springelement 50 a and the annular grooves 114 a causes the spring elements 50a to directly contact the arc surface of the annular groove at only twopoints 120. Furthermore, this configuration also ensures that the springelements 50 a will be centered axially in the annular grooves 114 a, andthat the spring action of the spring elements 50 a will serve to returnthe spring elements 50 a, along with the associated disc 8, to acentered position in the annular groove should any axially appliedmechanical shock tend to move the disc 8 and spring elements 50 a awayfrom the axially centered position in the annular groove.

Because FIG. 17-1 shows a cross section at the middle portion of thespring element 50 a, the inner diameter 8 a of the disc 8 can be seen tonot contact the outer radial surface 58 a of the spring element 50 a,while the operative surfaces of the disc 8 are still constrained betweenthe inner axial surfaces 60 of the spring element 50 a.

FIG. 17-2 is a sectional view similar to that of FIG. 16-2. That is, itshows a sectional view of the spindle motor hub 110, spring element 50 aand disc 8 near an end portion of the spring element 50 a. In thefigure, it can be seen that the inner radial surface 56 a of the springelement 50 a is radially spaced from the annular groove 114 a, while theouter radial surface 58 a of the spring element 50 a directly bears onthe inner diameter 8 a of the disc 8. Because of the arcuate shape ofthe outer radial surface 58 a of the spring element 50 a actuallycontacts the inner diameter 8 a of the disc 8 only at the two points122, thus contributing to the axial centering of the disc 8 relative tothe spring element 50 a. Again, if the dimensional tolerance necessaryto insert the disc 8 between the inner axial surfaces 60 of the springelement 50 a were to allow axial shifting of the disc 8 relative to thespring element 50 a due to axially applied mechanical shock, the springaction of the spring element 50 a would work to return the disc 8 to anaxially centered position relative to the spring element 50 a. Thus fromFIGS. 17-1 and 17-2, it is apparent that, since the disc 8 is fixedlylocated axially relative to the spring element 50 a, and since thespring element 50 a is fixedly located axially relatively to the annulargroove 114 a in the spindle motor hub 110, the axial position of thedisc 8 relative to the spindle motor hub 110 is firmly established.

From the foregoing, it is apparent that the present invention isparticularly well suited and well adapted to achieve the objects setforth hereinabove, as well as possessing other advantages inherenttherein. While particular configuration is of the present invention havebeen disclosed as example embodiments, certain variations andmodifications which fall within the envisioned scope of the inventionmay be suggested to one of skill in the art upon reading thisdisclosure. Therefore, the scope of the present invention should beconsidered to be limited only by the following claims.

What is claimed is:
 1. In a disc drive comprising: a spindle motorhaving a rotatable hub; at least one disc; and means for mounting saidat least one disc to said hub; the improvement comprising: improvedmeans for mounting said at least one disc to said hub.
 2. The disc driveof claim 1, wherein said improved means for mounting said at least onedisc to said hub comprises a means for maintaining said at least onedisc in a fixed predetermined position relative to the hub despitedifferential thermal expansion and large mechanical shocks.
 3. In amethod of mounting a disc on a hub of a disc drive, said methodcomprising the steps of: (1) providing a hub of a disc drive, said hubhaving a lower end at which a flange is located, an upper end, and adisc-receiving portion of the hub axially extending from the flange tothe upper end; (2) lowering a disc toward the flange of the hub from theupper end of the hub; and (3) mounting the disc to the disc-receivingportion of the hub; the improvement comprising: mounting the disc to thedisc-receiving portion of the hub in a manner such that a predeterminedradial position relative to the hub is maintained rigidly fixed despitedifferential thermal expansion and large mechanical shocks.
 4. In amethod of mounting a disc on a hub of a disc drive, said methodcomprising the steps of: (1) providing a hub of a disc drive, said hubhaving a lower end at which a flange is located, an upper end, and adisc-receiving portion of the hub axially extending from the flange tothe upper end; (2) lowering a disc toward the flange of the hub from theupper end of the hub; and (3) mounting the disc to the disc-receivingportion of the hub; the improvement comprising: mounting the disc to thedisc-receiving portion of the hub with an improved means for mounting adisc to a hub.
 5. The method of claim 4, wherein said improved means formounting a disc to a hub comprises a means for maintaining said disc ina fixed predetermined radial position relative to the hub despitedifferential thermal expansion and large mechanical shocks.
 6. Themethod of claim 4, wherein said improved means for mounting a disc to ahub comprises a disc mounting system comprising: one or more springelements, having a substantially C-shaped axial cross-section and formedas an arc of a circle, having a curvature along their lengths, at anouter radial contact surface thereof, both before and after finalassembly, greater than or equal to the radius of the inner diameter ofthe discs, mounted to an inner diameter of the discs with at least aportion of the open C-shaped axial cross-section axially overlapping theinner diameters of the discs, the spring elements also including aninner radial surface near middle portions of the spring elements bearingdirectly against the hub and the outer radial contact surface near endportions of the spring elements bearing directly against the innerdiameter of the discs to radially position the discs relative to thehub.
 7. A method of preventing radial shifting of a data disc relativeto a hub of a disc drive assembly, despite differential thermalexpansion and despite large mechanical shocks, said method comprisingthe steps of: (1) providing a hub of a disc drive, said hub having alower end at which a flange is located, an upper end, and adisc-receiving portion of the hub axially extending from the flange tothe upper end; (2) lowering a disc toward the flange of the hub from theupper end of the hub; and (3) mounting the disc to the disc-receivingportion of the hub with an improved means for mounting a disc to a hub.8. A method of mounting a disc on a rotatable hub of a spindle motor ofa disc drive, said method comprising the steps of: (1) providing arotatable hub of a spindle motor of a disc drive, said hub having alower end at which a flange is located and an upper end, adisc-receiving portion of the hub axially extending from the flange tothe upper end; (2) lowering a disc toward the flange of the hub from theupper end of the hub; and (3) mounting the disc to the disc-receivingportion of the hub with a disc mounting system comprising: one or morespring elements, having a substantially C-shaped axial cross-section andformed as an arc of a circle, having a curvature along their lengths, atan outer radial contact surface thereof, both before and after finalassembly, greater than or equal to the radius of the inner diameter ofthe discs, mounted to an inner diameter of the discs with at least aportion of the open C-shaped axial cross-section axially overlapping theinner diameters of the discs, the spring elements also including aninner radial surface near middle portions of the spring elements bearingdirectly against the spindle motor hub and the outer radial contactsurface near end portions of the spring elements bearing directlyagainst the inner diameter of the discs to radially position the discsrelative to the spindle motor hub.